1. Field of the Disclosure
The present invention relates to control a vehicle air-conditioner, particularly during vehicle deceleration fuel cut-off.
2. Description of the Related Art
Recently, there have been proposed and developed various fuel cut-off systems which are designed to reduce exhaust emissions and fuel consumption by cutting fuel supply to the engine cylinder or cylinders through the fuel cut-off control. The fuel cut-off control is frequently performed under certain required engine/vehicle operating conditions, such as during vehicle deceleration, during coasting, or during down-hill operation. Vehicle deceleration fuel cut-off is defined as the fuel cut-off control while the vehicle is decelerated.
On the other hand, many cars are equipped with automatic transmissions with so-called lock-up torque converters which act to mechanically couple the engine crankshaft to the transmission output shaft. When a lock-up device incorporated in the lock-up torque converter assumes its converter state (corresponding to a lock-up clutch release position), the engine crankshaft and the transmission output shaft are coupled via fluid in the torque converter in normal operation. When the lock-up device assumes its locked-up state (corresponding to a lock-up clutch engagement position), the engine crankshaft and the transmission output shaft are directly coupled to each other by a mechanical connection (via the lock-up clutch being engaged), thus disabling or locking up the torque converter. The converter state will be hereinafter referred to as a “lock-up OFF state,” whereas the locked-up state will be hereinafter referred to as a “lock-up ON state.”
The four engine rotation speeds are defined (from the high side) as Nrls1: a lockup clutch disengaging engine rotation speed when the air compressor 1 is driven; Nrcv1: a fuel supply recovery engine rotation speed when the air compressor 1 is driven; Nrls2: a lockup clutch disengaging engine rotation speed when the air compressor 1 is not driven; and Nrcv2: a fuel supply recovery engine rotation speed when the air compressor 1 is not driven.
The command signal for disengaging lock-up clutch occurs while coasting (“coast driving”) at the engine rotation speed between Nrls1 and Nrcv2 when the compressor receives a demand to be on according to the temperature of vehicle compartment becoming high. The conventional control system cancels fuel cut-off and turns on the compressor for the air-conditioner at the moment when the lock-up clutch has actually disengaged. If the system cancels fuel cut-off at the same moment as the command signal for disengaging lock-up clutch, a torque shock is generated because of disengagement delaying mechanically. Fuel supply is resumed with the lockup clutch being in an engaged state, and an output torque of the engine rapidly increases and is directly transmitted to the transmission via the lockup clutch due to resumption of fuel supply. Thus, a torque shock called a recovery shock is generated, thereby imposing discomfort on a driver and a passenger(s). Accordingly, the conventional control system described in Patent Document 1 cancels fuel cut-off after the delay of disengagement.
[Patent Document 1]
Japanese Patent No. 4337633